Unbox Therapy is back and this time around, they have tested the alleged rear panel belonging to the iPhone 6s. Pictured above: Apple's iPhone 6 (R) and iPhone 6 Plus (L) phones are shown together at a Verizon store in Orem, Utah Photo: George Frey/Getty Images

The iPhone 6 made record-breaking sales for Apple since going on sale last year. But it may not be able to repeat that in the final three months of 2015, according to a KGI Securities research note cited by Taiwanese site Apple Daily.

KGI's latest forecasts place iPhone sales in the fourth quarter between 65 and 75 million units, a negative to flat outlook for the Apple smartphone. In comparison, Apple sold 74.5 million iPhones during that period last year, largely due to the pent up demand for the iPhone 6. KGI predicts the iPhone 6S may not receive the same reception as the iPhone 6 for two reasons: a weakened Chinese economy and the smartphone’s latest feature -- the pressure-sensitive Force Touch screen -- may not be compelling enough for consumers to upgrade.

China has largely been cited as a driving force behind Apple’s strong iPhone 6 sales. But Beijing's move to devalue its currency on Tuesday could be a potential dent in future sales.

“China’s sudden devaluation confirmed market concerns over China’s economic growth,” Fubon analyst Arthur Liao told the Wall Street Journal. “We expect weaker consumer demand for iPhones in China and Apple may raise its product prices later if China continues to devalue its currency.” Though China’s economy has taken a downturn, Apple CEO Tim Cook has said in the past that he expects the country to become its largest market in the coming years.

Raising prices overseas isn’t unusual for Apple. Through 2015, it raised prices in several countries, largely in part due to a strong U.S. dollar, according to MacRumors.

Beyond Force Touch, the iPhone 6S may come with an A9 chip, thicker back case, improved camera and 2GB of memory. Apple is expected to announce the smartphone alongside new iPads and a revamped Apple TV on September 9.